The present invention generally relates to an automatic sipe forming machine for forming sipes (or sipings or fine or microscopic cuts) on a circumferential tread face of a new tire or a retreaded tire for the purpose of improving its resistance to skid.
Conventionally, in sipe forming methods, it has been arranged that an operator manually forms grooves on a tread face to a predetermined depth by the use of a knife while placing a scale on the tread face. However, the known sipe forming methods are undesirable due to their entire manual operations that require several hours for forming sipes on one whole tread face and the operation itself is dangerous, while non-uniformities or irregularities of pitch, depths, angles and shapes of the sipes are likely to occur.
Meanwhile, in order to automate sipe forming operations of this kind, a sipe forming machine is disclosed in, for example, Japanese Patent Publication No. 37947/1976 (Tokkosho No. 51-37947). However, this prior art sipe forming machine has such inconveniences that the machine is complicated in structure and high in production cost, while it is not easy to change pitches, angles, depths, etc. of the sipe.
In order to solve the above described problems, there was proposed in Japanese Patent Publication No. 5660/1981 (Tokkosho No. 56-5660) an automatic sipe forming machine which is simple in structure and low in manufacturing cost and in which it is easy to adjust or change pitches, angles, depths and shapes of the sipes. The known automatic sipe forming machine generally comprises a sipe forming apparatus and a feed apparatus. The sipe forming apparatus further comprises a cutter mechanism including at least one disc cutter rotated by a motor, a crank mechanism for reciprocating the cutter mechanism in a sipe forming direction, and an eccentric cam mechanism for reciprocating, in response to the reciprocation of the cutter mechanism in the sipe forming direction, the cutter mechanism in a vertical direction orthogonal to the sipe forming direction. Meanwhile, the feed apparatus further comprises a feed mechanism for intermittently feeding onto a table, in response to the sipe forming movement of the cutter mechanism, a material to be subjected to sipe forming, a vertical feed mechanism for moving the table vertically, and a pivotal mechanism for pivoting the table. However, the known automatic sipe forming machine is designed to form sipes on the flat surface of a sheet-like precured tread for a retreaded tire. Consequently, this known automatic sipe forming machine is undesirable in that the machine is not capable of directly forming sipes on a circumferential tread face of a new tire or a retreaded tire.